ALLIES OF THE EARTHWORM 231 



There may be more than one generation of females produced 

 in the spring and summer from large eggs, which undergo 

 development while attached near the tail of the parent (Fig. 

 114, 4). These eggs develop parthenogenetically (see p. 34). 

 The large eggs always produce females. Under certain con- 

 ditions some small eggs are formed. These develop with- 

 out fertilization into males. In the autumn the females form 

 " winter eggs," which are fertilized by spermatozoa from the 

 males. The fertilized eggs lie dormant through the winter 

 and develop into females in the spring. 



Members of the class to which Brachionus belongs (class 

 Motif era) are found in bodies of water, both salt and fresh, 

 all over the world. Certain species live in swamps, others at 

 the bottom of deep water, others still at the surface. No 

 matter how great the distance, the same species appears to 

 be present in situations that have approximately identical 

 conditions. This is accounted for partly by the fact that the 

 eggs will endure drying in the mud, and in that condition 

 may be scattered over wide areas by being carried on the 

 feet of birds, or by being blown about by the wind. Thus 

 they have the opportunity of developing in places exactly 

 suited to them. The phylum is called Trochelmin'thes (Gr. 

 troches, wheel; helmins^ worm). 



Plumatella. There are many animals which, in their habit 

 of living attached to some object throughout life, resemble 

 plants. Some of them live in a mass composed of many 

 individuals, so closely connected with one another that we 

 give the name "colony "to the entire collection. In the case 

 of Plumatel'la re' pens (Fig. 115) the individual zooids (mem- 

 bers of the compound organism) are connected by a system 

 of branching, but the vital organs of each are not connected 

 with those of any other zooid. A colony of Plumatella grows 

 in a small, roughly branched mass around a dead submerged 

 twig in fresh-water ponds. 



